Machines, including on and off-highway haul and vocational trucks, wheel loaders, motor graders, and other types of heavy machinery generally include a multi-speed, bidirectional, mechanical transmission drivingly coupled to an engine by way of a hydraulic torque converter. The hydraulic torque converter multiplies and/or absorbs torque fluctuations transmitted from the engine to the transmission by allowing slippage between a crankshaft of the engine and an input shaft of the transmission. The hydraulic torque converter is rotationally connected to and driven by the crankshaft via a splined interface.
Although the splined connection adequately transmits rotational power from the engine to the hydraulic torque converter and vice versa, because of terrain variations over which the machines travel and/or the loads to which the machines are exposed, translational shocks (i.e., sudden and/or violent axial and radial motion or force) transmitted from wheels or tools of the machine travel to the engine travel through teeth at the splined connection to the torque converter and, in reverse direction, from the torque converter's spline teeth to the engine's spline teeth. As a result, the teeth at the splined connection must be over designed for additional strength, hardened to prevent wear, massive and expensive, especially when the machine is exposed to very rough terrain.
One way to minimize tooth wear at the splined connection between an engine and a torque converter may be to isolate translational movements of the engine from the torque converter, which is described in U.S. Pat. No. 5,234,278 (the '278 patent) issued to Hall, III et al. on Aug. 10, 1993. Specifically, the '278 patent discloses a drive connection having a crankshaft to which is secured a conventional flex plate and a flywheel. The flywheel includes inner spline surfaces, an annular extension, and a plurality of tapered slots formed in the annular extension. Each slot has an opening formed in an end face of the annular extension. The drive connection also includes a torque converter input shell having a housing and a splined drive ring that cooperate to form an annular groove. The splined drive ring engages and is rotationally driven by the inner spline surfaces of the flywheel. A retainer ring is located within the annular groove formed by the housing and splined drive ring, and includes radially extending tabs that engage the slots of the flywheel through the openings in the annular extension. In this arrangement, the flex plate minimizes the transfer of axial motion and force between the engine and torque converter, while the retainer ring secures the splined members from relative axial displacement during operation of the associated engine and torque converter. By minimizing the transfer of axial motion and force, and by securing the splined members from relative axial displacement, the component life of the spline teeth may be enhanced.
Although the drive connection of the '278 patent may reduce spline tooth wear, the reduction may be minimal and expensive. Specifically, the tabs of the retaining ring only provide axial isolation for the spline teeth and, in some situations, relative radial translation between the splined teeth (i.e., separation between the teeth and re-engagement in the radial direction) can also be damaging. And, because the tabs maintain engagement with the flywheel and the torque converter housing (i.e., no gap exists therebetween such that preloading of the crankshaft is established), the amount of motion and force isolation may be minimal. In addition, the geometry of the tabs, because of the generally planar nature thereof, may only be suitable for low strength application. Further, the cost of the retaining ring, the groove formed by the housing and splined drive ring, and the open slots in the flywheel may be expensive to fabricate, difficult to assemble, and prone to improper assembly.
The drivetrain of the present disclosure solves one or more of the problems set forth above.